Add uv_library_shutdown() and uv__threadpool_cleanup() functions, introduce
UV_UDP_MMSG_CHUNK and UV_UDP_RECVMMSG flags, document cpu_times fields in
milliseconds, adjust priority constants for IBM i PASE, widen ansi_parser_state
to unsigned short on Windows, refactor async spin loop with sched_yield() and
eventfd support on Linux, add ARM yield in cpu_relax(), implement
uv__process_title_cleanup() on BSD and Darwin, replace CoreFoundation
dependency with darwin-stub.h, and fix accept4 detection for FreeBSD ≥10.
Dario Vladović